Kanchan
Kanchan 「嵌張」 is a wait pattern that completes with the middle number of a sequence.
| Kanji | 嵌張 |
|---|---|
| English | Closed wait, Middle wait |
| Fu | 2 fu |
| Tile types waiting | 1 sided wait |
| Tiles available | 4 tiles |
| Pattern example |
  |
| Tenhou.net example | Kanchan |
Pattern
Fu
Kanchan is awarded 2 fu upon winning. A closed hand winning by ron automatically becomes mangan, if it scores 4 han.
Ryankan
A ryankan ("double closed wait") is an extended form of a kanchan, only available before reaching tenpai. A ryankan shape is composed of three tiles that are each 2 apart, such as:
| Pattern |    |
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|---|---|---|---|
| Tiles to complete | |
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A ryankan is effectively the same as having 2 different kanchans; it waits for 8 tiles of two types (4 tiles per type).
However, you cannot enter tenpai with a ryankan. If you would reach tenpai without completing the ryankan, you'd have to discard one of its three tiles, turning it back into a weak kanchan wait.
Example hand with ryankan shape:
With the example hand above, if you drew 
, you would have to discard either or to enter tenpai. You end up with a bad wait, but with one major advantage - a ryankan always forms a suji trap. Here, if you discarded the 6s, you would wait on the suji 3s, thus making it more likely for others to deal in. This is why a suji of the riichi declaration tile is considered more dangerous.
Strategy
Kanchan is considered to be a "bad wait", because it can only wait for a maximum of 4 tiles. Thus, they are worse for hand development. Like the other bad waits, kanchan can be used to suji trap opponents.
In general, inner kanchans > outer kanchans > penchans when it comes to tile efficiency. See below for details.
Inner vs Outer Kanchan
There are two different types of kanchan: inner and outer.
| Type | Tiles | |||
|---|---|---|---|---|
| Inner | |
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| Outer | |
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Inner kanchans are generally superior to outer kanchans because they are easier to upgrade.
- A
kanchan can be upgraded by drawing 
(turning into ) OR 
(turning into ). It can also be turned into a ryankan when drawing either 
or 
.
- A
kanchan can only be upgraded by drawing . It can be turned into a ryankan when drawing only.
An inner kanchan can be upgraded by twice the amount of tiles, so inner kanchans are overall stronger. Note that an inner kanchan waits on a middle tile. Middle tiles are harder to win with; an inner kanchan is worse to keep at tenpai than an outer one.
Kanchan vs Penchan
While kanchan and penchan wait on the same number of tiles, a kanchan is considered better to keep, because a kanchan has more upgrades. This is similar to how inner kanchans are better than outer kanchans.
- A kanchan can be upgraded by drawing , turning it into a (two-sided) ryanmen.
- A penchan cannot be upgraded to ryanmen on its own. It must first draw a , turning it into a kanchan, then draw the to get a ryanmen.
As a kanchan requires 1 drawn tile to be upgraded to a ryanmen, but a penchan requires 2 drawn tiles, the kanchan is superior to keep before tenpai. In addition, only a kanchan can be turned into a ryankan shape, adding another advantage. However, once you reach tenpai, both kanchan and penchan become effectively identical.